The Leaders in Teaching 2020 study provides a unique opportunity to understand student numeracy scores in relation to their teachers and the schools they attended prior to school closures. It links 4,020 student numeracy assessments from Secondary 3 students in 100 schools, to a range of other data sources including: detailed information about school-level characteristics, data from surveys with up to eight STEM teachers per school, and data from school leader surveys. Numeracy assessment scores were collected using the instruments developed for the Learning Achievements in Rwandan Schools (LARS III) exercise, a nationally representative literacy and numeracy assessment designed for students in Primary 6 and Secondary 3. The numeracy assessment for the Leaders in Teachers 2020 study was conducted at the start of school year, in February/March 2020, prior to the closing of schools due to COVID-19. During the assessment, students were also asked questions about their individual characteristics (e.g., age and gender); family composition; the literacy levels of their parents; household asset ownership; time spent on chores, homework and other activities; and their academic history. This study explores how variation in numeracy assessment scores for Secondary 3 pupils at the start of the school year links to key student- and school-level characteristics.